1. Field of the Invention
This invention generally relates to a method for manufacturing an assembly of one-way clutch and its housing, and, in particular, to a method for manufacturing an assembly of an either an inner or outer ring of a one-way clutch and its housing, such as a stator or a torque converter, and its resulting structure.
2. Description of the Prior Art
Referring first to FIG. 2, there is schematically shown the overall structure of a torque converter 2 to which the present invention can be advantageously applied. As shown, the torque converter 2 includes a drive plate 1 through which a drive power is transmitted to the torque converter 2 from a power source, such as an engine. The torque converter 2 also includes a pump impeller 3, a turbine runner 4, a stator 5, an output shaft 6, a stationary shaft 7, a power output gear 8, and a one-way clutch 11, which includes an outer ring 9, an inner ring 10 and a pair of retainers 12 and 13. The stator 5 is typically made of an Al alloy by die casting or injection molding, and the outer ring 9 is typically comprised of alloy steel or carbon steel for a mechanical structure.
FIGS. 3a through 3c show one prior art method for manufacturing an assembly of a one-way clutch and its housing. In this case, a plurality of inwardly projecting keys are formed on the inner surface of the stator 5, for example, by machining, such as broaching, and a plurality of key grooves 9a are formed in the outer peripheral surface of the outer ring 9, each extending axially from one side to the other, by machining or forging. Then, the outer ring 9 is fitted into the stator 5 with its key grooves 9a in alignment with the respective keys of the stator 5. According to this method, because of the fitting accuracies required for the outer diameter of outer ring 9 and the inner diameter of stator 5, the machining cost tends to be expensive. Besides, structurally, the outer ring 9 tends to be large in thickness so that the resulting structure becomes larger in diameter. Thus, it is not possible to make the entire structure compact in size, which is extremely disadvantageous.
FIGS. 4a through 4d show another prior art method for manufacturing an assembly of a one-way clutch and its housing. In accordance with this method, a smooth surface is provided in the inner peripheral surface of stator 5 and a serrated structure 9b is provided, for example, by knurling at the outer peripheral surface of outer ring 9 of a one-way clutch. Then, the outer ring 9 is press-fitted into the bore of the stator 5. As different from the previous approach, this method allows to provided a structure having a reduced outer diameter; however, there is a limit in making the thickness of stator 5 thinner because of possible breakage due to press-fitting process and this process tends to be expensive because of involvement of knurling and press-fitting processes.
In order to obviate the disadvantages of the above-described prior art methods, Japanese Patent Post-examination Pub. No. 63-18050 teaches to provide projections or grooves at one side of an outer ring of a one-way clutch and have this outer ring built into a stator when forming the stator by casting. However, in the resulting structure of this approach, a mechanical connection is present only at one side of the outer ring of a one-way clutch, so that its structural integrity is a relatively low level and its width tends to become excessive.